The invention relates to a device for trapping at least one chromatography peak of a chromatography flow in a system comprising a LC-device and a NMR-detector.
Such a device is known from EP 1 001 263 A1.
A device of the afore-mentioned kind is generally used in liquid chromatography (LC) for trapping and concentrating single chromatography peaks of a chromatography flow, which, for example, have been previously separated in a liquid chromatography separating unit. Trapping and concentrating single chromatography peaks is a known technique for supporting the relatively weak sensitivity of nuclear magnetic resonance (NMR) analysis to which the chromatography peaks are submitted after separation in the LC separating unit for further investigation.
Although the NMR sensitivity is improved constantly, every further improvement is needed. To increase the amount of a separated chromatography peak, several techniques are known. One of them is the so-called solid phase extraction (SPE). In this technique the separated peak is trapped (absorbed) on a chromatographic post column. Using an appropriate treatment of washing and preparing the post column, it will be possible to trap the same chromatographic peak more than once and to concentrate or to accumulate it. Using a back flush option and an optimized desorbing solvent, broad separated trapped peaks will be flushed out as a substantially sharpened peak, in an extent up to a factor of 4. Both effects, the multiple adsorbing and the optimized peak shape are helpful to achieve better results with the NMR.
Lee Griffith and Rob Horton described in their article xe2x80x9cOptimization of LC-NMR III-increased signal-to-noise ratio through column trappingxe2x80x9d in Chem., Vol. 36, 104-109, 1998, a successful hyphenation of LC-SPE-NMR. They positioned one trapping column between some manual working valves. This construction showed the gain of sensitivity that can be reached with such a system.
In the document EP 1 001 263 A1 mentioned before, a high-performance liquid chromatography apparatus and a process for conversion of mobile phase enabling a trace amount of sample for NMR analysis to be efficiently separated and prepared are disclosed. The method comprises steps of separating target ingredients from the sample by high-performance liquid chromatography, trapping the target ingredient in a trapping column using a different mobile phase, replacing water by deuterium oxide and eluting this target ingredient from the trapping column using deuterated solvent other than deuterium oxide.
All the devices for trapping chromatography peaks known up to now, however, suffer from the disadvantage that they are not flexible in use and are difficult to be integrated in existing LC-NMR systems. Further, automatic software-controlled operation is not possible with these known systems. In any case, manually or offline-driven hardware components are used.
It is, therefore, an object of the present invention to improve a device of the kind mentioned at the outset in that way that the device is more flexible in operation and more flexible in integrating in an existing liquid chromatography system coupled to an analysis detector.
According to the present invention, this object is achieved with a device for trapping at least one chromatography peak of a chromatography flow in a system comprising a LC-device and a NMR-detector, wherein said trapping device is connected to said LC-device and to said NMR-detector, said trapping device comprising:
a plurality of trapping columns arranged on a column carrier;
an inlet capillary and an outlet capillary, said trapping columns being separately and selectively connectable to said inlet and said outlet capillary;
said column carrier further comprising a first connecting capillary connected to said inlet capillary and a second connecting capillary connected to said outlet capillary, and each of said trapping columns comprising a first capillary connectable to said first connecting capillary and a second capillary connectable to said second connecting capillary in a sealed fashion, said first connecting capillary being detachable from said inlet capillary and said second capillary being detachable from said outlet capillary,
wherein said column carrier is removable as a whole with said trapping columns mounted thereon from said trapping device.
The device according to the present invention is more flexible, because a plurality of chromatography peaks of the chromatography flow can be trapped in the plural trapping columns. Full automation of the device according to the present invention is possible, because the single trapping columns can be selectively connected to the inlet and outlet capillary. Further, multiple trapping of the same sample component of the chromatography flow in the same trapping column is also possible after different components have been trapped in other trapping columns. The device according to the present invention renders it possible to run a chromatography in a totally closed system.
The column carrier comprises a first connecting capillary connected to the inlet capillary and a second connecting capillary connected to the outlet capillary, wherein each trapping column comprises a first capillary connectable to the first connecting capillary and a second capillary connectable to the second connecting capillary in a sealed fashion.
The first and second connecting capillary of the column carrier serve as a joint between the trapping column of interest and the remaining part of the device. The trapping column of interest can be exactly positioned relative to the first and second connecting capillary of the column carrier. By virtue of the first and second connecting capillaries, which preferably are immovable, only the trapping columns and their first and second capillaries have to be movable parts of the column carrier.
Further, the first connecting capillary is detachable from the inlet capillary and a second connecting capillary is detachable from the outlet capillary.
This feature has the advantage that the column carrier can be configured as a removable part of the device so that the column carrier can be removed from the device after single peaks of the chromatography flow are trapped in the trapping columns.
Further, the column carrier is removable as a whole with the trapping columns mounted thereon from the device.
This feature has the advantage that a plurality of column carriers can be provided which can be exchanged. This can be useful if the user of the device needs different trapping columns of varying type, e.g. depending on sample polarity, or if the trapping is done in a different location than the subsequent analysis. The column carrier can be stored for several days before the trapped chromatography peaks would be desorbed into the destination detector. In connection with the aforementioned embodiments, the necessary information about the status of each trapping column is stored in a memory and can be read out directly by the device according to the present invention after mounting the column carrier.
In a preferred embodiment, each trapping column, which is not being connected to the inlet capillary and to the outlet capillary, is closed in a sealed fashion.
This feature has the advantage that the influence of the environment is practically not existing. Oxidation processes of the same peaks due to contact with air, decomposition due to light and pollution with dust is excluded.
In a further preferred embodiment, the columns are distributed in a series and the column carrier comprises a drive for moving the selected trapping column in a position for connection with the inlet capillary and the outlet capillary.
This feature has the advantage that the device according to the present invention can be operated without manual interaction, if an appropriate control, in particular a software control, is provided for operating the drive. The drive can be configured as an electrical motor.
In this connection it is preferred, if the column carrier comprises a ring, on an outer periphery of which the trapping columns are disposed, wherein the ring is rotatable.
A construction of the column carrier in form of a ring has the advantage that a great number of trapping columns can be arranged on the column carrier in a space-saving manner. Further, with this configuration the overall dimensions of the column carrier can be held small. However, it is also possible to configure the column carrier as a bar or a slider, if there is no need to save space.
In a further preferred embodiments the first and second connecting capillaries have their open ends mounted on a sealed slider, wherein the ends of the connecting capillaries are directed radially outwardly, and open ends of the first and second capillaries of each trapping column are directed radially inwardly for connection with the open ends of the first and second connecting capillaries.
This feature has the advantage that each trapping column can be exactly connected to the first and second connecting capillaries in a sealed fashion which guarantees the tightness of the connection between the trapping column of interest and the remaining part of the device.
In a further preferred embodiment, the column carrier comprises a control unit for controlling the position of each trapping column with respect to the inlet and outlet capillaries.
This feature enables full automatic operation of the column carrier in order to position the trapping column of interest exactly with respect to the inlet and outlet capillaries.
In a further preferred embodiment, the column carrier comprises a memory for storing data of the current condition of each trapping column.
This feature has the advantage that the actual state of each trapping column can be stored in the memory. This feature is, in particular, useful in case that the column carrier is exchangeable so that information on the state of each trapping column is not lost after removal of the column carrier from the device, because the memory board is integrated in the carrier.
In a further preferred embodiment, the trapping columns have different trapping properties.
By this feature, the flexibility of the device according to the present invention is further enhanced, because different components which need different trapping conditions can be trapped in the appropriate trapping columns, while only one column carrier is needed.
In a further preferred embodiment, the device further comprises at least one first add up flow pump for pumping the chromatography flow by means of at least a first eluent into the selected trapping column, the add up flow pump being connected to the inlet capillary.
This feature improves the trapping conditions and increases the trapping efficiency of the component in the trapping column, whereby the sensitivity gain for the destination detector is increased, too. The add up flow pump pumps the weaker desorbing solvent of the chromatographic separation and is preferably able to add two to four times the volume of the separation applied flow.
In this context it is preferred, if the add up flow pump is connected to the inlet capillary via a switchable valve for connecting and disconnecting the add up flow pump to the inlet capillary.
This feature has the advantage that the add up flow pump can be operated as a permanently working pump, while the pump flow can be interrupted by switching the valve between the open and the closed position.
In a further preferred embodiment, the device further comprises at least a first desorbing pump for pumping at least a second eluent into a selected trapping column for pushing out a peak trapped therein.
The desorbing pump is used to desorb trapped peaks from the trapping columns, for example, to a destination detector, e.g. a NMR detector. The used desorbing eluent is preferably the stronger eluting solvent of the chromatography. The desorbing solvent can be used in deuterated form to avoid large solvent signals and to achieve a better sensitivity, this means that the whole chromatography can be run completely non-deuterated, which has advantages for mass spectroscopy (no molecular ion distribution will be generated for molecules with exchangeable protons) and for the running costs, as normal LC-NMR uses at least one solvent in deuterated form. If the desorbing pump is able to provide more than one solvent, a deuterated weak desorbing solvent can be used to get rid completely of the protonated chromatography solvents. In this case the add up flow solvent mentioned before can be a protonated solvent, because the protonated solvent can be flushed out by the deuterated desorbing solvent provided by the desorbing pump.
In a further preferred embodiment the desorbing pump is connected to the outlet capillary.
This feature has the advantage that the desorbing step can be carried out in the back flush mode, i.e. the desorbing flow is directed in the opposite direction as the flow in the trapping action. By the back flush mode the peak sharpness can be enhanced further, in total up to a factor of 4, using all features mentioned herein.
In a further preferred embodiment, at least one control detector is provided which is disposed in a capillary line selectively connectable to the inlet capillary or the outlet capillary.
This detector can advantageously be used in connection with a peak recognition software for checking in the trapping mode of the device, if the peak to be trapped in the selected trapping column is breaking through. When desorbing a trapped peak from a selected trapping column, a perfect calculation for the timing and positioning of the desorbed peak can be done with this detector.
In a further preferred embodiment, a means for heating and/or cooling the trapping columns is provided.
This feature enables a temperature control of the trapping columns. For preparing each trapping column, it can be useful to heat the trapping columns to a certain temperature in order to be able to try the trapping columns more effectively. With respect to instable peaks trapped in the trapping columns, it can be useful to cool the trapping columns to be sure that the trapped peaks do not precipitate. The means for heating and/or cooling the trapping columns can be provided in the column carrier itself for direct temperature control or in a compartment in which the column carrier is disposed for an indirect temperature control.
In a further preferred embodiment a gas flow source is connectable to the trapping columns.
This feature has the advantage that by means of the gas flow the trapping columns can be dried in a quick and effective manner. In some applications it is helpful to dry the trapping columns after each trapping in order to increase their capacity, in particular in cases of multiple trapping of the same chromatography peak in multiple identical separations in the same trapping columns.
Further, in case that the destination detector is an IR spectrometer, drying will help to get rid of the water which is disturbing a large part of the observable spectrum.
In a further preferred embodiment, each of the trapping columns is connectable to the inlet and outlet capillary again after having been disconnected therefrom for multiple trapping of a same species of chromatography peak in one and the same column.
This feature has the advantage to increase the peak amount on a trapping column which in some applications is urgently needed to achieve the desired detection level, in particular in case of a subsequent NMR detection.
Further features and advantages will be apparent from the following description and the attached drawings.
It will be understood that the above-mentioned features and those to be discussed below, are not only applicable in the given combinations, but may also be employed in other combinations or taken alone without departing from the scope of the present invention.